An apparatus for electrosurgical sclerosing of body tissue

The invention relates to a high-frequency power applying device for thermal sclerosing of body tissue with a high frequency generator are connected to the at least two electrodes, of which at least one electrode is inserted into body tissue, and with a measuring and calculating device, which is designed, the impedance or the ohmic resistance between the two electrodes, between which flows a therapeutic high frequency current to determine, and connected to the measuring and calculating device control means for varying the output power. The measurement and calculation apparatus is the first derivative during a high-frequency current application from the time course of the impedance or ohmic resistance. The control means reduces the output power significantly when said time derivative exceeds a positive threshold, which is characteristic of an impending tissue desiccation, and provides the output power back to the original power if the first derivative of a negative threshold for a sufficient rehydration of the body tissue is characteristic exceeds toward positive values.